Method for manufacturing cold-forged extruded aluminum alloy rod

ABSTRACT

A method for manufacturing a cold-forged extruded aluminum alloy rod includes the steps of: (A) preparing a primary material and a cold extrusion apparatus including a cold extrusion die and a cold extrusion punch corresponding in position to the cold extrusion die; (B) processing the primary material to form a solid preform; (C) subjecting the preform to a homogeneous annealing; (D) testing the hardness of the preform; (E) immersing the preform in a tank containing a lubricant for a predetermined time, (F) applying talcum powder on the preform; and (C) subjecting the preform to cold forging to thereby forming the cold-forged extruded aluminum alloy rod.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims priority of Taiwanese Invention Patent Application No. 109146653, filed on Dec. 29, 2020.

FIELD

The disclosure relates to a method for manufacturing a cold-forged extruded aluminum alloy rod by cold forging and cold extrusion.

BACKGROUND

A conventional connecting structure of a bicycle is generally made by hot forging and hot extrusion in response to the shape and structural strength requirements. Specifically, a material subjected to hot forging and hot extrusion is first heated in a furnace to a temperature above the recrystallization temperature, followed by a processing step for shaping. Hot forging and hot extrusion not only require a furnace that can withstand high temperature and a material-taking equipment, but also incur a high capital expenditure due to quick wearing of the hot forging and hot extrusion dies and large consumption of energy.

SUMMARY

Therefore, an object of the present disclosure is to provide a method for manufacturing a cold-forged extruded aluminum alloy rod by cold forging and cold extrusion that can alleviate at least one of the drawbacks of the prior art.

According to this disclosure, a method for manufacturing a cold-forged extruded aluminum alloy rod includes the steps of:

(A) preparing a primary material having a block shape and made of an aluminum alloy material, and at least one cold extrusion apparatus including a cold extrusion die, and a cold extrusion punch corresponding in position to the cold extrusion die;

(B) processing the primary material to form a solid preform that extends along an axis and that has a first end surface intersecting the axis, a second end surface opposite to the first end surface along the axis, and an outer circumferential surface interconnecting outer circumferential edges of the first end surface and the second end surface, the preform having a length extending from the first end surface to the second end surface, and an outer diameter measured across the outer circumferential surface;

(C) subjecting the preform to a homogeneous annealing which involves heating the preform in a furnace to a temperature ranging from about 410° C. to 510° C., and then removing the preform from the furnace after the furnace is cooled to a temperature ranging from about 160° C. to 200° C. at a cooling rate of 10° C. per hour;

(D) testing the hardness of the preform, the hardness being equal to or below 60 degrees measured on Rockwell Hardness F scale;

(E) immersing the preform in a tank containing a lubricant for a predetermined time;

(F) applying talcum powder on the first end surface, the second end surface and the outer circumferential surface of the preform after the preform is immersed in the lubricant; and

(G) subjecting the preform to cold forging which involves positioning the preform in the cold extrusion die, after which the cold extrusion punch is operated to strike against the preform to thereby form the cold-forged extruded aluminum alloy rod, the cold-forged extruded aluminum alloy rod being a solid rod that extends along the axis, and having a first side surface intersecting the axis, a second side surface opposite to the first side surface along the axis, and an outer circumferential surface interconnecting outer circumferential edges of the first side surface and the second side surface, the cold-forged extruded aluminum alloy rod having a length that extends from the first side surface to the second side surface thereof and that is longer than the length of the preform.

BRIEF DESCRIPTION OF THE DRAWINGS

Other features and advantages of the disclosure will become apparent in the following detailed description of the embodiment with reference to the accompanying drawings, of which:

FIG. 1 is a flow chart, illustrating the steps involved in a method for manufacturing a cold-forged extruded aluminum alloy rod according to an embodiment of the present disclosure;

FIG. 2 is an exploded cross-sectional view of a first cold extrusion apparatus of the embodiment, illustrating how a preform is formed into a first cold-forged extruded aluminum alloy rod having first dimensions;

FIG. 3 is an exploded cross-sectional view of a second cold extrusion apparatus of the embodiment, illustrating how the first cold-forged extruded aluminum alloy rod is formed into a second cold-forged extruded aluminum alloy rod having second dimensions;

FIG. 4 is an exploded cross-sectional view of a third cold extrusion apparatus of the embodiment, illustrating how the second cold-forged extruded aluminum alloy rod is formed into a third cold-forged extruded aluminum alloy rod having third dimensions;

FIG. 5 is a schematic view, illustrating how the preform is formed into the third cold-forged extruded aluminum alloy rod of the embodiment; and

FIG. 6 is an exploded cross-sectional view of an advanced forming apparatus of the embodiment, in which a patterned cold-forged extruded aluminum alloy rod is formed.

DETAILED DESCRIPTION

Referring to FIG. 1, a method for manufacturing a cold-forged extruded aluminum alloy rod according to an embodiment of the present disclosure includes steps 1 to 7.

In step 1, referring to FIGS. 2 and 5, in combination with FIG. 1, a primary material 1 and three cold extrusion apparatuses 2, 2′,2″ are prepared. The primary material 1 has a block shape and is made of an aluminum alloy material, for instance, but is not limited to, AL6066 aluminum alloy and AL7050 aluminum alloy. Each of the cold extrusion apparatuses 2, 2′, 2″ includes a cold extrusion die 10, 10′, 10″, and a cold extrusion punch 20, 20′, 20″ corresponding in position to the cold extrusion die 10, 10′, 10″. The cold extrusion die 10, 10′, 10″ has a top surface 11, 11′, 11″ and a die cavity 12, 12′, 12″ extending inwardly and downwardly from the top surface 11, 11′, 11″. In this embodiment, the die cavity 12, 12′, 1″ of each cold extrusion apparatus 2, 2′, 2″ has a stepped shape and tapers from top to bottom. The die cavity 12 has a bottom portion having a first cavity diameter (d1). The die cavity 12′ has a bottom portion having a second cavity diameter. (d2) smaller than the first cavity diameter (d1), and the die cavity 12″ has a bottom portion having a third cavity diameter (d3) smaller than the second cavity diameter (d2).

The cold extrusion punch 20, 20′, 20″ of each cold extrusion apparatus 2, 2′, 2″ includes a base 21, 21′, 21″, and a ram 22, 22′, 22″ extending downwardly from the base 21, 21′, 21″. The ram 22, 22′, 22″ of each cold extrusion apparatus 2, 2′, 2″ has a rod shape with a bottom edge thereof being chamfered.

The ram 22 has a first outer diameter (D1) corresponding to the first cavity diameter (d1). The ram 22′ has a second outer diameter (D2) corresponding to the second cavity diameter (d2) and smaller than the first outer diameter (D1). The ram 22″ has a third outer diameter (D3) corresponding to the third cavity diameter (d3) and smaller than the second outer diameter (D2).

In step 2, with reference to FIGS. 1 and 2, the primary material 1 is processed to form a solid preform 1′ that extends along an axis (X) and that has a first end surface 101 intersecting the axis (X), a second end surface 102 opposite to the first end surface 101 along the axis (X), and an outer circumferential surface 103 interconnecting outer circumferential edges of the first and second end surfaces 101, 102. The preform 1′ has a length (L) extending from the first end surface 101 to the second end surface 102, and an outer diameter (D0) measured across the outer circumferential surface 103.

In step 3, the preform 1′ is subjected to a homogeneous annealing which involves heating the preform 1′ in a furnace to a temperature ranging from about 410° C. to 510° C., and then removing the preform 1′ from the furnace after the furnace is cooled to a temperature ranging from about 160° C. to 200° C. at a cooling rate of 10° C. per hour.

In step 4, the hardness of the annealed preform 1′ is tested. The hardness of the preform 1′ is equal to or below 60 degrees measured on Rockwell. Hardness F scale (HRF). The testing of the hardness of the preform 1′ is performed at multiple points of the outer circumferential surface 103 of the preform 1′ and at equal intervals along the axis (X).

In step 5, the preform 1′ is immersed in a tank containing a lubricant (not shown) for a predetermined time. In certain embodiments, the lubricant has a free total acidity (TA) concentration ranging from 40% by weight to 50% by weight at a working temperature ranging from 80° C. to 100° C. The lubricant used may be boron nitride. In other embodiments, the lubricant, for instance, a liquid grease, has a viscosity index (VI) of equal to or above 170, a flash point of equal to or above 240° C., a pour point of equal to or above −24° C. and a fire point of equal to or above 255° C.

In step 6, the first end surface 101, the second end surface 102 and the outer circumferential surface 103 of the preform 1′ are applied with talcum powder after the preform 1′ is immersed in the lubricant.

In step 7, with reference to FIGS. 2 and 5, the preform 1′ that has been immersed in the lubricant and applied with talcum powder is subjected to cold forging. The preform 1′ is positioned in a top opening of the die cavity 12 of the cold extrusion die 10, after which the cold extrusion punch 20 is operated to strike the ram 22 against the preform 1′, thereby forming a first cold-forged extruded aluminum alloy rod 100 that has first dimensions. The first cold-forged extruded aluminum alloy rod 100 is a solid rod that extends along the axis (X), and has a first side surface 110 intersecting the axis (X), a second side surface 120 opposite to the first side surface 110 along the axis (X), and an outer circumferential surface 130 interconnecting outer circumferential edges of the first and second side surfaces 110, 120. The first cold-forged extruded aluminum alloy rod 100 has a length (L1) that extends from the first side surface 110 to the second side surface 120 thereof and that is longer than the length (L) of the preform 1′, and an outer diameter (D′) smaller than the outer diameter (D0) of the preform 1′.

In this embodiment, a step of subjecting the first cold-forged extruded aluminum alloy rod 100 to undergo steps 3 to 7 may be further conducted. Referring to FIG. 3, in combination with FIG. 5, in this step, the first cold-forged extruded aluminum alloy rod 100 is positioned in a top opening of the die cavity 12′ of the cold extrusion die 10′, after which the cold extrusion punch 20′ is operated to strike the ram 22′ against the first cold-forged extruded aluminum alloy rod 100, thereby forming a second cold-forged extruded aluminum alloy rod 100′ that has second dimensions different from the first dimensions. The second cold-forged extruded aluminum alloy rod 100′ is also a solid rod that extends along the axis (X), and has a first side surface 110′ intersecting the axis (X), a second side surface 120′ opposite to the first side surface 110′ along the axis (X), and an outer circumferential surface 130′ interconnecting outer circumferential edges of the first and second side surfaces 110′, 120′. The second cold-forged extruded aluminum alloy rod 100′ has a length (L2) that extends from the first side surface 110′ to the second side surface 120′ thereof and that is longer than the length (L1) of the first cold-forged extruded aluminum alloy rod 100, and an outer diameter (D″) smaller than the outer diameter (D′) of the first cold-forged extruded aluminum alloy rod 100.

In this embodiment, a step of subjecting the second cold-forged extruded aluminum alloy rod 100′ to undergo steps 3 to 7 may be further conducted. Referring to FIG. 4, in combination with FIG. 5, in this step, the second cold-forged extruded aluminum alloy rod 100′ is positioned in a top opening of the die cavity 12″ of the cold extrusion die 10″, after which the cold extrusion punch 20″ is operated to strike the ram 22″ against the second cold-forged extruded aluminum alloy rod 100′, thereby forming a third cold-forged extruded aluminum alloy rod 100″ that that has third dimensions different from the second dimensions and the first dimensions. The third cold-forged extruded aluminum alloy rod 100″ is also a solid rod that extends along the axis (X), and has a first side surface 110″ intersecting the axis (X), a second side surface 120″ opposite to the first side surface 110″ along the axis (X), and an outer circumferential surface 130″ interconnecting outer circumferential edges of the first and second side surfaces 110″, 120″. The third cold-forged extruded aluminum alloy rod 100″ has a length (L3) that extends from the first side surface 110″ to the second side surface 120″ thereof and that is longer than the length (L2) of the second cold-forged extruded aluminum alloy rod 100′, and an outer diameter (Da) smaller than the diameter. (D″) of the second cold-forged extruded aluminum alloy rod 100′. For example, the outer diameter (D′) may be 45 mm, the outer diameter (D″) may be 22 mm, and the outer diameter (Da) may be 6 mm. It should be noted that the number of the cold extrusion apparatuses 2, 2′, 2″ prepared in step 1 corresponds to the number of times that steps 3 to 7 is repeated.

Thus, by utilizing the above-mentioned consecutive steps 1 to 7 of the present disclosure and by repeating steps 3 to 7 twice, the primary material 1 can be formed into the third cold-forged extruded aluminum alloy rod 100″. The third cold-forged extruded aluminum alloy rod 100″ can avoid the defects caused by metal heating, can obtain high precision and surface quality, can improve the hardness and strength of a workpiece, and has a large deformation resistance during cold forging. By processing the primary material 1 into the preform 1′ in step 2, the third cold-forged extruded aluminum alloy rod 100″ is not required to undergo precision machining, and the cold extrusion apparatuses 2, 2′, 2″ axe not easily worn out. In addition, the homogeneous annealing process in step 3 can improve plasticity of the preform 1′, the first cold-forged extruded aluminum alloy rod 100 and the second cold-forged extruded aluminum alloy rod 100′, so that in the cold forging process in step 7, residual stress of the first cold-forged extruded aluminum alloy rod 100, the second cold-forged extruded aluminum alloy rod 100′ and the third cold-forged extruded aluminum alloy rod 100″ can be reduced, and the homogenization of the composition and structure thereof can be improved. Furthermore, both steps 5 and 6 can provide a lubricating effect to facilitate the subsequent cold forging process.

Therefore, the method for manufacturing the cold-forged extruded aluminum alloy rod 100, 100′, 100″ of the present disclosure does not require high temperature hot forging equipment and material-taring equipment. In addition, the processing of the primary material 1 into the preform 1′ in step 2 not only can improve precision of the cold-forged extruded aluminum alloy rod 100, 100′, 100″, but also can reduce wearing out of the cold extrusion dies 10, 10′, 10″ of the cold extrusion apparatuses 2, 2′, 2″ so as to prolong the service life thereof. Furthermore, an overall power consumption and the manufacturing cost can be reduced.

It is worth mentioning that, in this disclosure, a step 8 may be provided, in which, referring to FIG. 6, an advanced forming apparatus 3 is prepared for forming the third cold-forged extruded aluminum alloy rod 100″ into a patterned cold-forged extruded aluminum alloy rod (100 a) according to the requirement. The advanced forming apparatus 3 includes a forming die 31 having a molding die cavity 311, and a forming punch 30 corresponding in position to the forming die 31. The forming punch 30 includes a forming fixing seat 34, and a forming ram 32 extending downwardly from the forming fixing seat 34.

In step 8, the cold-forged extruded aluminum alloy rod 100″ is positioned in the molding die cavity 311, after which the forming punch 30 is operated to strike the forming ram 32 against the third cold-forged extruded aluminum alloy rod 100″ to thereby form the patterned cold-forged extruded aluminum alloy rod (100 a).

It should be noted herein that in step 5 of this disclosure, the predetermined time for immersion of the preform 1′ into the lubricant depends on the number of the preform 1′. When the number of the preform 1′ is one, the predetermined time is 4 to 5 minutes. When there are a plurality of the preforms 1′, the predetermined time may range from 25 to 35 minutes.

In sum, the method for manufacturing the cold-forged extruded aluminum alloy rod 100, 100′, 100″ by cold forging of the present disclosure has simple processing steps and equipments, is energy-saving, can effectively reduce the capital cost, and can improve the quality of the obtained cold-forged extruded aluminum alloy rod 100, 100′, 100″.

While the disclosure has been described in connection with what is considered the exemplary embodiment, it is understood that this disclosure is not limited to the disclosed embodiment but is intended to cover various arrangements included within the spirit and scope of the broadest interpretation so as to encompass all such modifications and equivalent arrangements. 

What is claimed is:
 1. A method for manufacturing a cold-forged extruded aluminum alloy rod, comprising the steps of: (A) preparing a primary material having a block shape and made of an aluminum alloy material, and at least one cold extrusion apparatus including a cold extrusion die, and a cold extrusion punch corresponding in position to the cold extrusion die; (B) processing the primary material to form a solid preform that extends along an axis and that has a first end surface intersecting the axis, a second end surface opposite to the first end surface along the axis, and an outer circumferential surface inter-connecting outer circumferential edges of the first end surface and the second end surface, the preform having a length extending from the first end surface to the second end surface, and an outer diameter measured across the outer circumferential surface; (C) subjecting the preform to a homogeneous annealing which involves heating the preform in a furnace to a temperature ranging from about 410° C. to 510° C., and then removing the preform from the furnace after the furnace is cooled to a temperature ranging from about 160° C. to 200° C. at a cooling rate of 10° C. per hour; (D) testing the hardness of the preform, the hardness being equal to or below 60 degrees measured on Rockwell Hardness F scale; (E) immersing the preform in a tank containing a lubricant for a predetermined time; (F) applying talcum powder on the first end surface, the second end surface and the outer circumferential surface of the preform after the preform is immersed in the lubricant; and (G) subjecting the preform to cold forging which involves positioning the preform in the cold extrusion die, after which the cold extrusion punch is operated to strike against the preform to thereby form the cold-forged extruded aluminum alloy rod, the cold-forged extruded aluminum alloy rod being a solid rod that extends along the axis, and having a first side surface intersecting the axis, a second side surface opposite to the first side surface along the axis, and an outer circumferential surface interconnecting outer circumferential edges of the first side surface and the second side surface, the cold-forged extruded aluminum alloy rod having a length that extends from the first side surface to the second side surface thereof and that is longer than the length of the preform.
 2. The method of claim 1, wherein in step (D), the testing of the hardness of the preform is performed at multiple points of the outer circumferential surface of the preform and at equal intervals along the axis.
 3. The method of claim 2, further comprising a step (H) after step (G), wherein step (H) involves repeating step (C) to step (G) at least once, and wherein the number of the cold extrusion apparatus prepared in step (A) corresponds to the number of times that step (C) to step (G) is repeated.
 4. The method of claim 3, wherein an advanced forming apparatus is further prepared in step (A), the advanced forming apparatus including a forming die that has a molding die cavity, and a forming punch corresponding in position to the forming die, the method further comprising a step (I) after step (H), wherein step (T) involves positioning the cold-forged extruded aluminum alloy rod in the molding die cavity, after which the forming punch is operated to strike against the cold-forged extruded aluminum alloy rod to thereby form a patterned cold-forged extruded aluminum alloy rod.
 5. The method as claimed in claim 1, wherein the aluminum alloy material for making the primary material in step (A) is AL6066 aluminum alloy.
 6. The method as claimed in claim 1, wherein the aluminum alloy material for making the primary material in step (A) is AL7050 aluminum alloy.
 7. The method as claimed in claim 1, wherein the predetermined time in step (E) is 4 to 5 minutes.
 8. The method as claimed in claim 1, wherein the lubricant used in step (E) has a free total acidity (TA) concentration ranging from 40% by weight to 50% by weight at a working temperature ranging from 80° C. to 100° C.
 9. The method as claimed in claim 3, wherein the lubricant; used in step (E) is boron nitride.
 10. The method as claimed in claim 1, wherein the lubricant used in step (E) is a liquid grease.
 11. The method as claimed in claim 10, wherein the lubricant used in step (E) has a viscosity index of equal to or above 170, a flash point of equal to or above 240° C., a pour point of equal to or above −24° C. and a fire point of equal to or above 255° C. 